Microwave based systems and methods are provided for obtaining carbonaceous compounds from polypropylene-containing products. In one example, embodiment, a method is provided for recovering at least one organic decomposition product from a polypropylene-containing product, the method comprising: placing the polypropylene-containing product in a reduction zone of a material recovery system; flowing an inert gas through the reduction zone from a reduction inlet to a reduction outlet to purge the reduction zone and maintain a positive pressure therein; applying electromagnetic wave energy from an electromagnetic wave generator to the reduction zone via a bifurcated waveguide assembly, while maintaining the polypropylene-containing product in a stationary position for at least a portion of the applying, to yield at least one gaseous organic decomposition product; and exhausting the at least one gaseous organic decomposition product from the reduction zone along with the inert gas through the reduction outlet.